| Effects of Ca alloying elements on electrochemical properties of Mg-based sacrificial anodes were evaluated. Potentiodynamic, galvanostatic tests, optical microscopy and XRD analyses were used to investigate the corrosion rate, efficiency, and surface analysis of anodes. Polarization data indicated that the alloying with Ca reduced the corrosion rates of magnesium anodes. The increased corrosion resistance generally improved anode efficiency. All anodes did not undergo passivation but demonstrated only active behavior. Corrosion morphology was changed from localized to uniform attack by the Ca alloying. Addition of Ca to the Mg anodes yielded increased driving potential and efficiency. Mg-Mn-Ca anodes had the highest efficiency and driving potential. The improved performance of Mg-Mn-Ca and Mg-Ca anodes was attributed to : (1) the homogeneous and refined microstructures by the addition of small amount of Ca, i.e., uniformity of anode consumption along grain boundaries (2) extremely electronegative potential of Ca. |
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